Published almost simultaneously, these very different books present a double view of Martin Kemp's original and often brilliant approach to the connection between science and art. Leonardo focuses on a single genius; Seen/Unseen pulls back the lens to investigate the nature of creativity thematically, using profiles of extraordinary artists/scientists over a span of 500 years. Kemp is intrigued by visual works that combine the skills of artist and scientist, often, but not always, in the same person; he calls himself a "historian of the visual."

Kemp's ideas may be familiar to readers of Nature who have followed his science and culture column. Currently professor of art history at the University of Oxford, he has produced a veritable library of books and articles about Leonardo. Away from his desk he organizes exhibitions, most recently one at the Victoria and Albert Museum in London; the beautiful, coffee table-size Leonardo da Vinci: Experience, Experiment and Design accompanied this exhibition. Kemp's text dovetails seamlessly with the often life-size reproductions of Leonardo's drawings, sketches, jottings and notes, providing insight into the artist's philosophy, mastery of geometry, and compassion.

Leonardo da Vinci has fascinated generations of artists, art critics and novelists. But few have been as absorbed as Kemp, who has walked in the master's footsteps through Italy and France. Kemp's name is synonymous with Leonardo scholarship. In a February New York Times account of the announcement of the possible discovery of a missing Leonardo masterpiece, The Battle of Anghiari--walled off but retrievable in the Palazzo Vecchio--the reporter gave weight to the claim by noting that Kemp strongly supported the investigation.

Leonardo is based on a "theme sheet," a miraculously recovered piece of folded paper (reproduced across two pages in the book) on which the artist began sketching and writing in 1490. Kemp explains the value of paper half a millennium ago--which meant that every inch was used--and he interprets the apparent chaos of sketches as a record of Leonardo's "laboratory for thinking." He tells us that there are about 6,000 surviving pages of the artist's notes and sketches.

Yet even for the keenly interested, Leonardo's notes, written in a mirror script, are difficult to decipher, and their dispersion on this theme sheet may not be deliberate. A finely drawn portrait of an old man merges with a delicate pair of trees, and the rest of the drawings, notes and designs bear no apparent relation to these sketches or to one another. The jottings, combined with references to the well-known paintings and models for machines, reveal a man of his time at home with geometry, though probably not mathematically prepared for the scientific revolution that was a century in the future. Ahead of his time in a visual way, however, Leonardo observed nature closely and drew "notes" from what he saw, from an autopsied heart to floodwaters and debris, believing that all knowledge had to be confirmed by observing natural phenomena. He must have had remarkable eyesight to capture motion as he did, as well as a rare ability to see mentally in three dimensions, one of the themes of Kemp's second book, Seen/Unseen.

Although Leonardo is not the heart of Seen/Unseen, he is the touchstone for much of Kemp's thinking and one of the "nodal" figures, men (mostly) who as both artists and scientists are the focus of each of its chapters. In "Wholes and Parts," for instance, Kemp identifies Charles Darwin as a man with one foot in the dynamic view of nature of the early 19th century, where men such as his grandfather Erasmus Darwin and artist George Stubbs saw "an animate nature in continual flux," and the other foot in the Victorian era, in which "Natural Selection itself represents the emergence of the 'fittest' theory into a very specific environment" that was familiar with the earlier worldview and thus receptive to his much more radical theory.